Converting an integer to double-byte hex using Python

Question

I need to take an integer (e.g. -200) and change it to hexadecimal (FF 38) and then to an integer 0-255 to send via the serial port. An example of this was:

-200 = hex FF38 = [hex FF] [hex 38] = [255] [56]

I tried to use struct.pack('>h', -200), but returned an invalid value. I also tried hex(), but this is also a negative hex value.

I do not know what else I should try.

Answer 1

>>> hex(struct.unpack('>H', struct.pack('>h', -200))[0])
'0xff38'

-200 2- int. unsigned 2- int. 65336, hex ff38

---

0-255, :

>>> struct.unpack('>BB', struct.pack('>h', -200))
(255, 56)
>>> struct.unpack('>BB', struct.pack('>h', 200))
(0, 200)

---

Requisite struct

Answer 2

:

hex(200 - (1 << 16)) #2 bytes -> 16 bits
Out[26]: '-0xff38'

int(hex(200 - (1 << 16))[-4:-2], 16)
Out[28]: 255

int(hex(200 - (1 << 16))[-2:], 16)
Out[29]: 56

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